1. Field of the Invention
The present invention relates to an engine having a plurality of superchargers.
2. Background Art
Conventionally, as an engine having a plurality of superchargers, an engine having a two-stage supercharging system is known. In the engine having the two-stage supercharging system, for example, turbines rotatively driven by receiving exhaust gas are arranged in one exhaust passage in series, and compressors pressurizing intake air are arranged in one intake passage in series. Bypass valves are provided in a bypass passage bypassing the exhaust gas from the upstream side to the downstream side of the turbines and a bypass passage bypassing the exhaust gas from the upstream side to the downstream side of the compressors, whereby the supercharging pressure can be limited by controlling the bypass valves (for example, see the Patent Literature 1).
However, conventionally, in the engine having the superchargers, only the control is performed in which the supercharging pressure is limited corresponding to the operating state of the engine based on detection signals from an intake air flow rate sensor and a supercharging pressure sensor. Therefore, in the engine having the two-stage supercharging system, it is difficult to secure the supercharging pressure corresponding to the operating state of the engine while limiting the rotational speed of each of the compressors constituting the superchargers to be within a high-efficiency range of the supercharger.    Patent Literature 1: the Japanese Patent Laid Open Gazette 2004-92646